About twenty years ago Hawking made the remarkable suggestion that the black
hole evaporation process will inevitably lead to a fundamental loss of quantum
coherence. The mechanism by which the quantum radiation is emitted appears to
be insensitive to the detailed history of the black hole, and thus it seems
that most of the initial information is lost for an outside observer. However,
direct examination of Hawking's original derivation (or any later one) of the
black hole emission spectrum shows that one inevitably needs to make reference
to particle waves that have arbitrarily high frequency near the horizon as
measured in the reference frame of the in-falling matter. This exponential
red-shift effect associated with the black hole horizon leads to a breakdown of
the usual separation of length scales, and effectively works as a magnifying
glass that makes the consequences of the short distance, or rather, high energy
physics near the horizon visible at larger scales to an asymptotic observer.Comment: 6 pages, 2 figs. summary of lectures presented by Erik Verlinde at
the 1994 Les Houches Summer School ``Fluctuating Geometries in Statistical
Mechanics and Field Theory.'' (also available at http://xxx.lanl.gov/lh94/ )
(based on work with Y. Kiem, K. Schoutens and H. Verlinde